The present invention relates to systems and methods for inducing infrared multiphoton dissociation of ions for mass spectrometry analysis. More specifically, the present invention relates to systems and methods for inducing infrared multiphoton dissociation of ions for mass spectrometry analysis by delivering infrared energy to an ion dissociation chamber via an infrared waveguide.
Infrared multiphoton dissociation (IRMPD) is increasingly being used to induce fragmentation of molecular ions to provide sequence/structural information for mass spectrometric characterization of biomolecules. See Stephenson et al., xe2x80x9cAnalysis of Biomolecules Using Electrospray Ionization-Ion Trap Mass Spectrometry and Laser Photodissociation,xe2x80x9d ASC Symp. Ser. 619:512-564 (1996), the entire contents of which are herein incorporated by reference. Unfortunately, finding materials that are suitable for the transmission of infrared energy has proven to be difficult. Today most infrared optical components are generally made of a Barium-fluoride (BaF) or a Zinc-Selenium (ZnSe) compositions that have special infrared-compatible coatings.
The present disclosure is directed at improved systems and methods for inducing infrared multiphoton dissociation of ions for mass spectrometry analysis. In an exemplary embodiment in accordance with present disclosure, the system has an ion dissociation chamber that has an ion storage area and an infrared waveguide that is coupled to the ion dissociation chamber. The infrared waveguide can be positioned to receive infrared energy (e.g., an infrared laser beam) generated by an infrared energy source and direct the infrared energy towards ions located in the ion dissociation chamber for the purpose of fragmenting the ions. The system may also include a focusing lens located between the infrared laser energy source and an end of the infrared waveguide. In certain exemplary embodiments, the infrared waveguide is a hollow fiber waveguides (HFWG). Some HFWGs have been shown to transmit high power infrared energy at 10.6 xcexcm in excess of 1000 Watts with minimal power loss which can make them suitable since IRMPD typically only employs about 2-20 Watts. In a preferred embodiment, the infrared waveguide can be comprised of a hollow fused silica body that has an optically reflective inner layer. The infrared waveguide preferably is flexible.
In other exemplary embodiments, the system may also include an aperture housing having an orifice located between an infrared laser energy source and an end of the infrared waveguide. The aperture housing may protect the end of the infrared waveguide from the harmful effects of the infrared energy. In some embodiments, the inner diameter of the orifice may be less than or equal to the hollow inner diameter of the infrared waveguide.
In yet other exemplary embodiments in accordance with the present disclosure, the system may also include a positional alignment system coupled an end of the infrared waveguide. The positional alignment system can control the location of the end of the infrared waveguide relative to an infrared energy beam.
In another exemplary embodiment, a system may further include an infrared transparent window coupled to an end of the infrared waveguide. The infrared transparent window may assist in maintaining a desired pressure within the ion dissociation chamber.
In certain exemplary embodiments in accordance with the present disclosure, an end of the infrared waveguide is aligned substantially orthogonally to a longitudinal axis of the ion storage area of the ion dissociation chamber. In other embodiments, an end of the infrared waveguide is aligned substantially parallel to the longitudinal axis of the ion storage area. While in yet other embodiments, an end of the infrared waveguide is aligned substantially non-orthogonally to the longitudinal axis of the ion storage area.
In other exemplary embodiments, the ion dissociation chamber can further include infrared reflective element to reflecting the infrared energy delivered by the infrared waveguide back towards the ion storage area.
In certain exemplary embodiments in accordance wit the present disclosure, the ion dissociation chamber can be an ion trap, an ion reservoir or an ion guide, such as a linear multi-pole ion trap or a cylindrical multi-pole ion trap.
Still other objects and advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description wherein several embodiments are shown and described. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not in a restrictive or limiting sense, with the scope of the application being indicated in the claims.